I have two SR2's, and had previously owned an SR1 and an SR3, in order to compare performance. I found the SR1 and 2 to be reasonably equal in sensitivity, but as noted above, the SR2's audio sounded a bit better, thx to the extra speaker. The SR3 was a price point Chinese assembly, the build quality and performance of which was noticeably lacking vs the earlier models, which were also made in China.

So overall, the SR2's are certainly the best of the run, and by that virtue would be of higher value than the other two models. The also seem to be available in greater abundance than the SR1, indicating that they probably sold better when they were available new.

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